Aggressiveness and Delinquency In Boys Is Linked to Lead in Bones

By JANE E. BRODY

Published: February 7, 1996

CRIMINALS may indeed be made, not born, and one of the ingredients could be childhood exposure to lead, according to the findings of a four-year study of young boys that is being published today.

The study, conducted among more than 800 boys attending public schools in Pittsburgh, showed that those with relatively high levels of lead in their bones were more likely to engage in aggressive acts and delinquent behavior than boys with less lead in their bones. Although none of the children in the study were suffering from lead poisoning, a direct relationship was found between the amount of lead in their leg bones and reports by parents, teachers and the children themselves of aggressive and delinquent behaviors.

The study, directed by Dr. Herbert L. Needleman, a psychiatrist at the University of Pittsburgh Medical Center who has done other research on the effects of lead, found that even after taking into account other predictors of delinquency, such as socioeconomic status, those with higher lead levels were more likely to engage in antisocial acts.

Such acts in childhood have been shown to be strong predictors of criminal behavior later in life, Dr. Needleman said in his report, which is appearing today in The Journal of the American Medical Association.

In an accompanying editorial, Dr. Terrie E. Moffitt, a psychologist at the University of Wisconsin in Madison who has studied the long-term consequences of antisocial behavior in children, wrote, "Measures of childhood antisocial behavior are reasonably accurate, broadly applicable and moderately predictive of adult violent crime and related outcomes such as alcoholism and domestic abuse."

In an interview, Dr. Needleman emphasized: "I'm not saying that lead exposure is the cause of delinquency. It is a cause and one with the biggest handle to prevention." He explained: "Lead is a brain poison that interferes with the ability to restrain impulses. It's a life experience which gets into biology and increases a child's risk for doing bad things."

Most previous studies of the effects of lead on child development have focused on intelligence scores and growth, and most have relied on levels of lead in the blood as an indicator of lead exposure. But, as noted by Dr. David Bellinger, a lead researcher at Boston Children's Hospital: "Bone lead levels may be more significant than blood lead because they are a measure of lead accumulation over a long period of time. A child could have high bone lead while his blood levels are not high at the time they are measured."

Dr. Bellinger said the Pittsburgh study "breaks new ground, opening the possibility that some of the violence in our society could be the result of preventable environmental pollution" by lead.

The study took into account various social and family factors that have previously been linked to delinquent behavior. These included nine measures reflecting maternal intelligence, socioeconomic status and child-rearing factors, such as the number of children in the family and the presence of two parents in the home. Also accounted for were the children's race and history of medical problems. Still, the lead-delinquency relationship held strong, the researchers reported.

Even when the children were grouped according to their scores on standard intelligence tests, the study found that those with higher lead levels scored higher on a checklist of childhood behavior problems, as assessed by parents and teachers.

The new findings extend in a scientific way earlier observations of a link between lead exposure and delinquent, violent or criminal behavior. More than 50 years ago, Dr. Randy K. Byers, who was a child neurologist at Boston Children's Hospital, linked acute lead poisoning in children to later "violent, aggressive behavioral difficulties, such as attacking teachers with knives or scissors."

In another study of 987 African-American boys and girls followed from birth to the age of 22, Deborah Denno, then a sociologist at the University of Pennsylvania, found that having had lead poisoning was "the strongest predictor of disciplinary problems in junior high school boys and the third strongest predictor of both juvenile and adult offenses."

Dr. Denno, now a lawyer at Fordham University in New York, said in an interview, "Lead had its own independent effect on delinquency and adult criminality, separate from I.Q."

Such observations encouraged Dr. Needleman and his colleagues to explore the role of "normal" lead exposures -- lead levels experienced by ordinary urban schoolchildren -- as a risk factor for antisocial behavior. Dr. Needleman explained that the peak age for lead accumulation in bones was from 13 to 30 months, when toddlers are walking about and repeatedly putting their hands in their mouths. Often, those hands are contaminated with dust that contains lead. At the time the youngsters in his study were so exposed, the average urban child had blood lead levels of 12 micrograms per deciliter of blood.

Dr. Needleman said that since the ban on leaded gasoline took effect, the average blood level had dropped to about 3.2 micrograms, which would suggest that today's children are less likely than the group Dr. Needleman studied to show toxic effects of lead on the brain. However, he added, large numbers of American children "continue to have lead burdens in the neurotoxic range."

In the latest national survey by the Federal Centers for Disease Control and Prevention, conducted from 1988 to 1991, 8.9 percent of children from 1 to 5 years old were found to have blood lead levels greater than 10 micrograms, a level the agency designates as potentially hazardous. The figure for non-Hispanic black children in that age group was highest, at 21 percent.

Chart: "Lead's Legacy" shows a correlation between lead and behaviorproblems in children.